Recently, attention has been focused on optical fibers mainly in communication fields. Particularly in the IT (Information Technology) field, a communication technique which employs the optical fibers is necessary to provide a high speed Internet network.
The optical fiber has features of (1) low loss, (2) high band, (3) small diameter and light weight, (4) non-induction, (5) resource saving, and the like. A communication system which employs the optical fibers having these features can considerably decrease the number of relays as compared with a communication system which employs conventional metallic cables, can be easily constructed and maintained, and can improve its economical efficiency and reliability.
Further, since the optical fiber can transmit not only light having a single wavelength but also light having a number of different wavelengths simultaneously, i.e., only one optical fiber can provide multiple transmission of light having a number of different wavelengths, it is possible to realize a large capacity of a transmission line capable of dealing with diversified purposes and deal with picture service and the like.
Therefore, in the field of the network communication such as the Internet, it is proposed that the use of optical transmission using optical fibers not only for the communication of a basic network but also the communication between the basic network and terminal device (a personal computer, a mobile, a game machine or the like) and the communication between the terminal devices.
When the optical communication is used for the communication between the basic network and the terminal device, an IC which processes information (signals) in the terminal device operates at an electric signal; therefore, the terminal device is required to include a unit that converts optical signal into an electric signal or vice versa such as an optical-to-electric converter or an electric-to-optical converter (which device will also be referred to as “optical/electric converter”, hereinafter).
For this reason, the conventional terminal device has mounted thereon separately, a package substrate on which an IC chip is mounted, and optical elements such as a light receiving element and a light emitting element which process optical signal, and electric wirings and the optical waveguide are connected to these elements, thereby performing signal transmission and signal processing.